if you have ALREADY graduated with your bachelors degree, when/if you take additional undergrad classes to statisfy premed requirements, how will your gpa be effected??
The grades you get in any UNDERGRAD courses will be factored into calculating your UNDERGRAD GPA. It doesn't matter if you've already graduated. Undergrad courses are undergrad courses.
That's true about all undergrad being calculated together, but that's not the end of the story:
You will receive numerous GPA calculations. Total undergrad, post bacc, science gpa, and graduate. So your post bacc classes will count for something.